While the invention of the above-noted patent utilizes a tripod arrangement of helve-head-mounted three spaced-apart roller surfaces positioned for bearing on an upright flat edge surface extending along an x-axis of a drafting board, the present invention while utilizing the same principal and arrangement also discloses another comparable embodiment, but together with additional problem-solving features directed to entirely different problems and difficulties facing a draftsman with the state of the art prior to the present invention.
Some of those problems and difficulties arise from the historical approach to drafting, using pin-pricks and the like on the paper on which drafting drawings are being applied, and making the drawing(s) and thereafter applying to the sheet a scale-data line of varying complexity. The complexity of ascertaining that the drawings during the drawing thereof remained in accord with proper and correct dimensional relationships of other portions of the drawing(s) required constant diligence and care, all contributing to increased difficulty in the drafting as well as requiring extended times periods of exacting work per drawing or portion thereof. Along with such problems of ascertaining that portions of drawings being drawn are of dimensions consistent with other portions already drawn, involve the precision use heretofore of a multiplicity of rules and the like to measure and compare distances and dimensions, particularly where fractional measurements and drawings-portions are required as a part of the entire drawing(s).
Also, heretofore, considered alone or in combination with the afore-mentioned problems or difficulties, simple or non-complex but precision-made drawing boards having inherent precision-engineered linearly extending x-axis and/or y-axis edges that may be relied on by a draftsman for use therewith of a T-square simply have not existed, although there have been various cumbersome and complicated devices affording a straight-guiding edge--such as the device of Beebe et al. U.S. Pat. No. 2,874,474 dated Feb. 24, 1959 that requires a specially-mounted plurity of brackets and guide-rail supported-thereon utilizable of solely a specific bearing-mechanism and drawing device disclosed in that patent as a substitute for the conventional T-square. Nothing along the nature noted-above of a simple to-scale drafting board has existed utilizable of any conventional T-square.
Considered alone, or together with the aforementioned problems, there has existed another momentous problem facing the draftsman over the ages, where scaled precision drawings are theretically required, with regard to T-squares. In particular, the open-throated T-square such as typically illustrated in the above-noted disclosure of above-noted U.S. Pat. No. 4,422,245 of which this is a continuation-in-part, over the years has come into wide use by draftsmen, but cannot be relied on for giving consistent measurement readings from time to time of intermittent reading or drawings based thereon, it has been discovered by the present inventor. Also, such open-throated T-squares have proven to be extremely fragile, readily subject to fracture of the open-throat structure of the helve head, fracturable or breaking as a result of a slight blow or bending or droping thereof accidentally, particularly in the environment of use by draftsmen active in industry in the making of tools, dies and the like where T-squares are typically metal to improve durability, but still not reliable for consistent nor accurate dimentions.
Also for the industrial draftsman who typically uses a sharppointed scriber for cutting into metal making scribing directly onto a metal surface, such metal objects rarely have a thickness comparable to that of a sheet of drafting paper, i.e. such metal objects have an upper surface elevated well-above the surface of the drafting board on which the metal object rests. This results in difficulty in maintaining the metal object in a non-shifting position as well as adding to difficulty of scribing on its upper metal surface.